The present invention is directed to an apparatus and method for directional well drilling. It is more specifically directed to a resilient wedge-shaped whipstock which is permanently set in proper location in a drill hole.
In the past, various types of drill deflecting devices called "whipstocks" have been provided for insertion within a drill hole. These devices are commonly required when the lower portion of the hole has become blocked due to equipment debris, such as a broken drill stem, which can not be readily removed. In some cases this obstruction necessitates starting a completely new well. However, whenever possible, it is desirable from a cost standpoint, to utilize as much of the original hole as possible and offset a new lower hole portion to bypass the obstruction. The whipstock allows the drill bit and stem to be deflected past the blocked hole to provide this necessary offset.
Numerous prior art provisions have been made for lowering and using a whipstock in the original hole and setting it mechanically. In these, however, the reliance has been placed on various mechanical expanding mechanisms for wedging and holding the whipstock in position. These types of devices are inherently expensive and contribute considerably to the drilling costs.
Conventional whipstocks are made of metal, the idea being to provide a wedge face which cannot be affected or crushed by the bit. However, this usually results in excessive costs from rapid drill bit deterioration and long drill-off times. The whipstock described herein has a softer surface that is deformable, yet tough, durable and resilient, thus, resistant to the crushing action of the drill bit. Thus, the drill bit is essentially unaffected by contact with the present invention and drill-off rates can be accomplished within a few minutes.
It has been recognized for years that some type of reliable inexpensive whipstock would be highly desirable. In addition, it would be desirable to have a whipstock which could be easily positioned within the hole without need for cementing and conveniently set to meet the desired directional drilling requirements.
In other cases, it is desirable to orient the drill stem both in angle and direction in order to obtain penetration of oil bearing formations at an optimum position. Directional drilling is also common where high dip angles of bedding planes may force a drill string off a desired path.
In all four of the above cases, a significant improvement over current methods is provided by this new and improved whipstock. Specifically, current methods of deviation (when not drilling off the bottom) often require cementing the hole to a depth above the junk or to a position where deviation is required. Cementing has significant actual costs, and more importantly usually requires a 24-48 hour cure time which results in rig down-time and considerable expense. The whipstock described herein obviates the need for cementing and it does not require rig down-time.
It is sometimes desired to form a multiplicity of feeder or side-track holes at the bottom of an oil well in order to increase the gathering capacity of the well. Such a "crow's foot" arrangement requires multiple directional drilling and removal of the whipstock used for each. The whipstock of this invention can be removed when desired by using a cutting drill to remove the tough polymer. Whereas the tough, resilient wedge of this whipstock is remarkably durable and wear resistant to a crushing type of star bit, it is still easily cut and removed by a sharp drill designed for cutting through plastics.
In mining exploration using core or side-track holes, the multiple downhole branching technique as described above can save expensive surface drilling and rig relocation by providing for several core sites from one upper drill hole. Removal of the whipstock would not be mandatory in this instance.
It is therefore an object of the present invention to provide such a whipstock which can be both easily and inexpensively manufactured and which would substantially reduce the expense involved when it is necessary to provide offset directional drilling.
It is a further object of the present invention to provide a directional drilling arrangement in which the device can be easily lowered into the hole and securely fixed in proper position.
It is a still further object of the present invention to provide a whipstock manufactured from relatively lightweight, inexpensive material which will provide continued operation after many drill bit passages and remain securely attached to the drill hole in its required position.
A further object of the present invention is to provide a whipstock which can be set in position and properly secured by the actual drill bit and drill stem used in the drilling operation without the requirement for additional lowering and placing of the equipment.
It is a further object of the present invention to provide a whipstock and components which can be securely adhered to each other in a compact cylindrical unit, and which can provide the desired results with a minimum of down-time for placement, setting and offset drilling.
It is a further object of this invention to provide a whipstock device which can be permanently set and drilled off even without the requirement for cement.
It is a still further object of this invention to provide a whipstock device which can be easily and quickly cut-out when desired so that multiple feeder holes can be accomplished at the bottom of an oil or gas well.